When a vehicle encounters a collision from the front, a vehicle occupant tends to be moved forward by inertia. When the vehicle occupant wears a seat belt, due to a restraining action of a shoulder belt or a hip belt, a movement forward of the vehicle occupant can be suppressed by a considerable level, even though there are some cases where the restraining action is insufficient
A vehicle occupant hip portion restraining device, which is constructed so as to limit the movement forward of the vehicle occupant being seated on a seat by raising a front end of a seat cushion instantly, to prevent the vehicle occupant being seated on the seat from being moved forward, when the vehicle speed is reduced rapidly due to a collision from the front or a like, is known by, for example, Japanese Patent Application Laid-open Nos Hei5-229378 and Hei10-217818, Great Britain Patent No. GB2357466, and a like. Additionally a vehicle occupant leg portion restraining device to protect the leg portion that moves forward, is disclosed in Japanese Patent Application Laid-open Nos. Hei8-40177 and Hei9-123857.
FIG. 13 shows one example of the vehicle occupant hip portion restraining device disclosed in Great Britain Patent No. GB2357466 as this kind of vehicle occupant hip portion restraining device. FIG. 13(a) shows a state before expansion and development of the vehicle occupant hip portion restraining device and FIG. 13(b) shows a state after expansion and development of the vehicle occupant hip portion restraining device. FIGS. 13(a) and 13(b) show a seat frame 1 and on a front portion of this seat frame 1 a concave portion 1a, having a concave shape from a top view, is formed. And on an upper face of the concave portion 1a, a metal sheet 2 is set to cover the concave portion 1a in a state of being stuck on the seat frame 1 by welding, adhering, or a like. In this conventional example an inflator bag 3 is formed of the frame 1 and the metal sheet 2 and the inflator bag 3 is configured so as to be filled with a gas generated from an inflator 4 in an internal space of it.
In a vehicle equipped with this vehicle occupant hip portion restraining device, at time of sharp reduction of speed of the vehicle due to a collision from the front or a like the inflator 4 operates and releases a high-pressure gas into the inflator bag 3. Then the metal sheet 2 making up of the inflator bag 3 expands and develops and raises a front portion of a seat cushion 6 so that a vehicle occupant M being seated on the seat can be prevented from being moved forward.
FIG. 14 shows an example of another vehicle occupant leg portion restraining device (also called as a knee air bag device). FIG. 14(a) shows a state before expansion and development of the vehicle occupant leg portion restraining device and FIG. 14(b) shows a state after expansion and development of the vehicle occupant leg portion restraining device. FIGS. 14(a) and 14(b) show an instrument panel 11, a cover panel 12, and an air bag module 13, which is mounted inside and formed on the back side of the cover panel 12. The air bag module 13 is equipped with an inflator bag 14 (an air bag main body) and an inflator 15 and a gas generated by the inflator 15 fills the inflator bag 14.
In a vehicle equipped with the vehicle occupant leg portion restraining device, at time of sharp reduction of speed of the vehicle due to the front collision or a like the inflator 15 operates and releases the high-pressure gas into the inflator bag 14. Then the inflator bag 14 is expanded and developed and pushes out the cover panel 12 so that a leg portion N of the vehicle occupant being seated on the seat is restrained by the cover panel 12; as a result, during the impact when the leg portion N collides with equipment in the vehicle can be reduced.
Incidentally, when the inflator bag used for this kind of vehicle occupant restraining device is constructed as a metal single good part, as shown in FIG. 15 conventionally, an inflator bag is configured of two pieces of metal sheets 21 and 22 being stuck together by the welding (A dotted line 23 shows a welding section.), furthermore, as shown in FIG. 16 conventionally, an inflator bag is configured as a bellows-type having a peripheral wall 25 being a bellows shape. Though the inflator bag, shown in FIG. 15, is difficult to ensure a developing stroke S and is inferior in the energy-absorption, because the size in the direction of height is limited, and more, it has a problem that development shape tends to become unstable. On the other hand, the inflator bag, shown in FIG. 16, is easy to ensure a developing stroke S, though, its processing is difficult, and also, it has a problem that the height when the inflator is shrinking can not be made small.
In view of the above, it is an object of the present invention to provide an inflator bag for a vehicle occupant restraining device, which is capable of being housed compactly, and of developing with a stable state securing an enough developing stroke, and of which the processing is easy, and a method of manufacturing the inflator bag.